Ornamental · Asparagaceae
Black Mondo Grass
Ophiopogon planiscapus 'Nigrescens'
Few plants come this close to true black, and a little sun keeps the leaves at their darkest.
Full sun
Every 3–7 days
USDA 6–9
6–12 in · 15–30 cm
Overview
Here is one of the rare plants with near-black foliage, and designers reach for it again and again. The arching, grass-like leaves start out deep green-purple and deepen as they mature, on an evergreen perennial that holds its color right through the year. Despite the look, it is no grass at all; it sits in the asparagus family and hails from Japan.
Think of it as a slow, well-behaved groundcover. It travels on short underground runners and grows by inches rather than feet, so it never bullies its neighbors. Run it along a path edge, slip it between stepping stones, or mass it across the front of a border for real punch.
Cold-hardy down to 0°F (-18°C), it asks for very little once it settles in. Give it decent soil, steady moisture, and enough light to keep those leaves dark, and it pays you back year after year.
Care
The short version: give it full sun to part shade for the blackest leaves, keep the soil rich and evenly moist but never waterlogged, and tidy away the old foliage in late winter.
Light
Aim for full sun to part shade to pull out the darkest leaves; sink it into deep shade and the color drifts toward green. In hot regions a touch of afternoon shade keeps it happy.
Water
Keep the soil evenly moist, watering roughly every 3 to 7 days during dry spells. It shrugs off drought once established, but steady moisture delivers the best color and growth.
Soil
Plant it in rich, humusy, well-drained loam on the slightly acidic side, pH 5.5 to 7.0, and work in compost at planting time for a strong start.
Temperature
It takes everything from 0°F (-18°C) up to about 95°F (35°C), covering zones 6 through 9. The foliage stays evergreen through the cold and springs back fresh in spring.
Humidity
Ordinary outdoor humidity is plenty, so there is no number to chase. Drainage matters far more than air moisture, and soggy ground is what does the damage.
Feeding
Feed lightly in spring with a balanced general-purpose fertilizer or some compost. This is an undemanding plant, and piling on the fertilizer does little for it.
Pruning
There is barely any work here. Shear off the tattered or winter-worn leaves in late winter before new growth starts, and the clump bounces back looking fresh.
Repotting
In a container, lift and divide it every 2 to 3 years before the roots crowd the pot. A thinning center or slowing growth is your cue that it is time.
Size & spacing
Each clump reaches 6 to 12 inches (15 to 30 cm) tall and spreads 8 to 12 inches (20 to 30 cm). Set plants a foot apart for distinct clumps, or tighter for quicker cover.
When to plant
This hardy perennial settles into zones 6 through 9, so plant it once and it sticks around. Get it in the ground in spring to hand it a full season to settle, then watch for the small bell-shaped flowers in summer, from July into August.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: spring
- Harvest: summer (July to August)
Hardiness
USDA hardiness zones: 6–9
Temperature: down to -23°C
Troubleshooting
This is an easygoing plant, and most hiccups trace back to either too much shade or too much water. Catch the early signs on the leaves and roots and jump on them quickly, before they spread.
Yellowing leaves and a clump that rots in wet soil
Roots that sit in standing water invite root rot, and once it takes hold the foliage yellows and flops. Dig down and check: rotted roots feel soft and look dark. Mix grit or compost in to open up drainage, ease back on watering, and replant the healthy divisions somewhere that drains freely.
Fix:
- Improve drainage by amending soil with organic matter or grit
- Reduce supplemental watering when soil stays wet
- Replant healthy divisions in a better-drained, raised, or amended site
Weak, slow regrowth after dividing
A slow grower bounces back slowly, so fresh divisions may sit quietly for a stretch before they start pushing new growth. Divide in spring to hand them a full season to settle before winter, keep the soil evenly moist while roots form, and give them time rather than digging them up again.
Fix:
- Divide in spring so plants have the full season to re-establish before winter
- Keep soil evenly moist while new roots form
- Allow extra time for recovery rather than disturbing again
Slow to spread and fill in as a groundcover
Patience pays off here, because filling in slowly is simply how this plant operates. It creeps outward on short stolons and takes several seasons to knit into a solid mat, so a thin, gappy look in the early years is completely normal. Want coverage sooner? Set new plants closer at about 4 inches apart, and divide established clumps to fill the bare patches faster.
Fix:
- Be patient and allow clumps to establish over several seasons
- Plant more closely (about 4 in apart) when a faster groundcover effect is wanted
- Divide established clumps to make more plants and fill gaps
Black leaves washing out toward green
That dramatic dark color runs on sunlight, so when leaves drift toward green the culprit is usually deep shade. Shift the plant to a brighter spot and the near-black tones come roaring back. In hot regions a little afternoon shade keeps it comfortable, but lean toward sun if you want the darkest leaves possible.
Fix:
- Move or transplant to a brighter, sunnier location
- In warm climates provide some afternoon shade but otherwise favor sun for color
Ragged, chewed leaves with slime trails
Ragged holes paired with telltale slime trails point straight to slugs and snails, which feed after dark in damp, shady corners. Head out with a flashlight in the evening and pick them off. Clear away leaf litter and other hiding spots, and reach for slug control only where the damage really starts piling up.
Fix:
- Hand-pick slugs and snails in the evening
- Remove debris and reduce excess moisture and hiding spots
- Use slug controls where pressure is heavy
Toxicity
Good news: it is not toxic. It belongs to the asparagus family, not the dangerous true lilies it sometimes gets mistaken for. The worst case is mild stomach upset from eating a lot, which makes it a great pick for homes with pets and kids.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Safe to share space with curious cats. A few nibbled blades might bring on a brief upset stomach, the same as any plant eaten in quantity.
Dogs None
No real danger for dogs, since the foliage carries no known toxin, though a big mouthful could leave one briefly queasy.
Horses Safe
Not toxic to horses, and free of the poisons found in the true lilies this plant gets confused with.
Rabbits Safe
Rabbits can graze without harm; nothing in the foliage is poisonous, and an occasional bite is perfectly fine.
Livestock Safe
No risk to livestock, with none of the compounds that trouble grazing animals.
Birds Safe
Safe for birds; backyard poultry can pick at the leaves and small fruit with nothing to worry about.
People Safe
No risk handling it or gardening with it; a stray taste does no harm beyond the mild upset any non-food plant might cause.
No special handling required; as with any plant, discourage pets from eating large quantities to avoid mild stomach upset.
Varieties
A handful of selections and look-alikes share the mondo grass name. Tell them apart by leaf color, flower habit, and fruit.
Ophiopogon planiscapus 'Nigrescens'
The classic black mondo grass. Arching, grass-like leaves push out green-purple and darken to a glossy near-black, ranking among the darkest foliage you will find on any perennial.
'Black Dragon' / 'Ebony Knight'
Trade names sold for the very same near-black foliage you get from 'Nigrescens'.
Ophiopogon japonicus (green mondo grass / dwarf lilyturf)
The common green-leaved species, with narrower leaves than Liriope, flowers mostly tucked down in the foliage, and blue fruit instead of black.
Black-leaved Liriope (lilyturf)
A whole different genus, Liriope, sporting broader leaves, flowers on upright spikes that rise above the foliage, and black fruit rather than the blue of green mondo grass.
Companions
Plant near
Chartreuse or gold-foliage plants (e.g., golden creeping Jenny, Hakone grass 'Aureola'): Bright lime/gold foliage gives strong color contrast against the near-black leaves.
Silver or gray foliage plants (e.g., lamb's ear, dusty miller): Silver tones highlight the dark foliage for dramatic contrast in borders and containers.
How to propagate
There is one reliable way to make more, and it keeps that prized dark color true every single time.
DivisionEasy
Spring · One growing season
Division is the way to go, since this plant will not come true from seed. Split an established clump in spring and every piece holds onto that prized black color, with a full season ahead to settle in. Figure on about one growing season for the divisions to root and fill out.
Myths
Black mondo grass is a true grass.
It is not a grass at all. This is Ophiopogon planiscapus, an asparagus-family plant that simply grows in a grass-like evergreen clump and plays the part convincingly.
It is the same plant as green mondo grass or lilyturf.
Easy to mix up, but they stand apart. Green mondo is the related Ophiopogon japonicus, while lilyturf belongs to the separate genus Liriope with broader leaves and flower spikes held above the foliage; black mondo's narrow leaves and hidden flowers give it away.